1. Technical Field
This invention relates to vehicle electronic modules. In particular, the invention relates to a system for safely accessing memory in a vehicle electronics system, uncorrupted by power system fluctuations or other hostile electrical environmental factors.
2. Related Art
The electronic technologies supporting and incorporated into cars, trucks, and other vehicles, driven by strong market demand, have matured rapidly and become quite powerful in a short time period. Vehicle electronics systems include fundamental electronic modules ranging from engine controllers to anti-lock braking systems. In addition, vehicle electronic modules now commonly adapt sophisticated consumer technologies to the vehicle, including global positioning systems, cellular telephones, and high quality stereo sound systems.
Some electronic modules that implement the vehicle electronics system are connected to a vehicle communication bus, and to a power source ultimately derived from the voltage provided by the vehicle battery. At each vehicle ignition cycle, the electronic modules initialize and begin internal diagnostic checks. The diagnostic results are then written into a long-term memory and may be beneficially used during the continuing operation of the vehicle, may be used as a significant source of troubleshooting information for mechanics, or may be used or for other reasons.
The vehicle ignition cycle generates a hostile environment for the electronic modules. As the electronic modules begin to draw power and initialize they may induce severe inductive spikes, low voltages, and high frequency noise onto the vehicle battery line and other parts of the wiring harness. Coupled with relay chatter, ignition cycling, and the effects of magnetic induction on the wiring harness, the electronic modules may experience a hostile environment that is not conducive to stable or reliable operation. The hostile environment often causes corrupted data to be written into the long term memories, thereby destroying the data and making the data useless for helping to achieve the benefits noted above.
A need has long existed for addressing the problems noted above and others previously experienced.